A die casting machine generally comprises a stationary platen and a movable platen. The stationary platen is fitted with a stationary die half. The movable platen is fitted with a movable die half. The movable platen is aligned with the stationary platen by tie bars. The movable platen can be advanced toward and away from the stationary die along these tie bars. Movement of the movable platen toward and away from the stationary platen during machine operation may be accomplished by hydraulic cylinder, a toggle clamping linkage, etc., as would be familiar to one of skill in the art.
A problem associated with die casting processes is thermal expansion of a casting die. Thermal die expansion is a phenomenon that is well known in the die casting art and, therefore, need not be explained in detail herein. Generally, however, the repeated formation of work pieces by the introduction of molten metal into a casting die increases the die temperature and leads to the thermal expansion thereof. While the extent of this thermal expansion may not seem significant from a purely dimensional standpoint, the die growth can nonetheless be sufficient to negatively affect or interfere with proper casting machine operation. More specifically, after die expansion, the previously set clamping position of the movable platen may result in excessive pressure on the casting die, which can lead to excessive force being exerted on the die, increased strain on the tie bars, and/or other problems.
Therefore, it is known to adjust the position of a movable platen to account for thermal die expansion, a process commonly referred to as making a die height adjustment (or something similar thereto). On most casting machines, a manual die height adjustment may be performed by a machine operator. Manual adjustment often consists of a trial and error movement of the movable platen to what is believed to be a proper clamping location. This is time consuming and performed outside full automatic operation of the die casting machine.
Newer die casting machines may offer automatic die height adjustment systems that are able to automatically compensate for thermal die expansion. However, such an automated feature was not generally available on older die casting machines. While it is sometimes possible to retrofit such a system to an older die casting machine, doing so is typically a costly option that must be purchased from the original equipment manufacturer. Known automated die height adjustment systems available from the various original equipment manufacturers are generally quite complex, utilizing encoders, linear scales, specialized controllers and specialized programming. Further, the electrical components of the original casting machines become obsolete, frequently requiring that they also be upgraded, redesigned or modified in order to accommodate a retrofit die height adjustment system. This also adds cost to such a retrofit.
Consequently, it can be understood from the forgoing discussion that it would be desirable to provide a system and method for inexpensively and simply performing an automatic die height adjustment so as to compensate for thermal die expansion. Preferably, such a system may be easily retrofit to an existing die casting machine. A system and method of the present invention has such capabilities.